help needed for LED array..

[civvie]

**broken link removed**
**broken link removed**

Hope this helps

 

[audioguru]

Many parts in the circuit are designed to light individual LEDs with 16mA.
It can light 3 LEDs in series at each output if the value of the 620 ohm resistors is reduced to keep the current at 16mA.

 

[civvie]

Thanks, that's a simple solution to getting more out of the circuit.
what value resistor would you recommend for the job?
can the LEDs be in parallel?
what voltage LEDs will work best?

 

[audioguru]

It is not simple to get 10 times the current from a circuit.

A resistor in series with 3 LEDs needs to be calculated properly with the total LED voltage and the supply voltage.

LEDs in parallel need to be matched because each lED is different. This circuit is designed for the current of only one LED not more.

10 red LEDs that are 1.8V each have a total voltage of 18V. 10 blue LEDs that are 3.5V each have a total of 35V. Plus additional voltage for the current-limiting resistor.
Are you going to re-design the circuit so that it works from a 38V supply?

 

[civvie]

Thanks again for all your help, it is very much appreciated.

On the circuit information documentation it says the circuit is "designed for a standard input level 750mv. In case of a lower input level, resistor R1 shall be replaced with a higher rating resistor. Dynamics is determined by the C3 capacitor. Supply voltage: in the range of 9 - 15 v"

The PSU I was going to purchase is 9v, 12v, 15v & 18V (switchable) 1200mA.

Would it be necessary to change R1 because it is 1200mA?
Would I expect to see a difference in brightness between 12v and 15v PSU? (12v ones are much cheaper)


I have accepted that this circuit is not designed for my application so I am treating it as a conceptual design and will live with its faults (LEDs that are not as bright as the could be, inconsistency in brightness across different coloured LEDs)

If it is a successful prototype and the band likes it, I will try to design are better and brighter version from the ground up. At the moment I'm pushed for time and I have already purchased four of the level meter kits so I will have to make do.

 

[audioguru]

The PSU I was going to purchase is 9v, 12v, 15v & 18V (switchable) 1200mA.

Would it be necessary to change R1 because it is 1200mA?

1200mA is the max continuous allowed current from the power supply. It has nothing to do with this circuit that will draw a max current of only 150mA.
R1 sets the gain of the circuit. increase the value of R1 for more gain so the LEDs will respond to a lower input signal level.

Would I expect to see a difference in brightness between 12v and 15v PSU? (12v ones are much cheaper)

The difference in brightness will be small.